Field of the Invention
The present invention relates to a laser processing apparatus which performs laser processing for a workpiece such as a semiconductor wafer held on a chuck table.
Description of the Related Art
In a semiconductor device fabrication process, a plurality of regions are partitioned by scheduled division lines arrayed in a grating on a front face of a semiconductor wafer having a substantially circular disk shape, and a device such as an IC or an LSI is formed in each of the partitioned regions. Then, by cutting the semiconductor wafer along the scheduled division lines, the regions in each of which a device is formed are separated from each other to fabricate individual semiconductor chips. As a method for dividing a wafer such as a semiconductor wafer along scheduled division lines, a technique has been put into practical use which performs ablation processing by irradiating a pulse laser beam of a wavelength having an absorbency to a wafer along scheduled division lines to form laser processed grooves and applying external force along the scheduled division lines along which the laser processed grooves, each of which serves as a start point of break, are formed to break the wafer.
A laser processing apparatus which performs the laser processing described above includes workpiece holding means for holding a workpiece, laser beam irradiation means for irradiating a laser beam upon the workpiece held by the workpiece holding means, moving means for moving the workpiece holding means and the laser beam irradiation means relative to each other, and alignment means for detecting a region to be processed of the workpiece held by the workpiece holding means (refer to, for example, Japanese Patent Laid-Open No. 2006-253432).